Handheld radio devices such as cellular (or mobile) phones, including so-called “smart” phones, have become commonplace and are used by large segments of the population in developed regions of the world. The preferred shape and form factors of these devices have changed over the years. Various form factors and features, both aesthetic and functional, have been tried with varying degrees of acceptance among consumers. One aspect of handheld radio device design that has become a convention is the lack of an obvious antenna. Early devices used large, screw-in antennas similar to those used on public safety two-way radios. Retractable antennas then became common. Presently, very few cellular phones have a noticeable antenna. Some devices use an entirely internal antenna, while others have used external elements that are styled to provide an aesthetic feature of the device in addition to operating as an antenna. Among design challenges associated with all of these antenna designs is the loading effect of the human body, and in particular how the user of the device holds and positions the device when talking. Depending on the design and how a user holds the device, and in particular where the user's skin makes contact with the device, the radiated efficiency of the antenna can change significantly, and in some cases this can be a factor in unintentional call disconnection.
Some manufacturers use an external antenna configuration where an externally protruding element of the device contains one or more antenna structures. In one particular handheld radio device presently available in the market the handheld radio device uses a metal bezel that appears to wrap around the sides of the device to form two separate antennas, operating in distinct frequency bands, realized in part by interrupting the bezel continuity with small gaps. However, this aesthetically appealing design suffered significant performance issues caused by user's hands making contact with the bezel antenna elements. As a result, the radio frequency performance was degraded to the point that radio connections were lost at an unexpectedly high rate, resulting in what is commonly referred to as “dropped calls.” Dropped calls result from the communication being terminated as a result of the radiated efficiency dropping so low that the cellular base station does not receive either sufficiently strong signal from the device, or because of unacceptably low data throughputs.
Accordingly, there is a need for an antenna design that hides the antenna while providing similar or better device aesthetics (for instance by making it possible to have an uninterrupted metal bezel), but is less prone to severe degradations in performance depending on how the user holds the device.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.